Stephen Moyer as Captain Von Trapp, Carrie Underwood as Maria in ‘The Sound of Music Live!”

Will Hart/NBC

Almost immediately after British actor Stephen Moyer wraps up his performance as Captain von Trapp on “The Sound of Music Live!” on NBC, he’s going to jump on a plane and head off to shoot the seventh and final season of “True Blood,” the HBO series in which he co-stars as vampire Bill Compton.

But if you think he’s working hard, he argues that his “Sound of Music” co-star Carrie Underwood works even harder.

“I’ve worked with my wife ["True Blood" co-star Anna Paquin] and Carrie Underwood is one of the hardest workers I’ve ever worked with in my life,” he says. “Carrie is right behind her I would say. I wouldn’t put her above my wife–you can’t do that!–but she’s right up there! Carrie’s a gifted girl–she never settles for anything but perfection.”

With producers calling his name to return to work, Moyer talked to Speakeasy via phone from the Long Island set of “The Sound of Music Live!,” which airs at 8pm tonight on NBC.

How did you get pulled into this project?

My agents rang me. I was in the middle of rehearsals for “Chicago” and my agents rang me….It was a straight offer. It was weird because I was expecting a phone call about another job, and so when my agents rang me, I was thinking “Ohh–I wonder if this is that call?” And it wasn’t, it was this call. At first I thought, “they’re doing what? Are they crazy?” But I went and met [executive producers Craig Zadan and Neil Meron] and spoke to [director] Rob Ashford on the phone and heard about what it was they were trying to achieve.

You attended the London Academy of Music and Dramatic Art. How did that training prepare you for this, if at all?

God! I don’t think anything can get you ready for something like this. That’s no disrespect to my alma mater. This is unique. This is TV and theater but it’s not either of them. It is its own extraordinary thing. The performance that goes out on that night is the performance that it will be…This is our first night. Our first preview is our closing night. That is a very unique situation to be in. It’s scary and exciting all at the same time.

Will you be playing the guitar for the song “Edelweiss”?

Yes, I’m playing the guitar.

How are your guitar skills?

I literally know about three chords.

That’s all you need to start a punk band.

Exactly right man! That’s all the Beatles had when they started off! I’ve managed to make those three chords stretch a long while. This is a completely different thing. Playing live, singing live is a completely different situation…I start the guitar solo and then the orchestra joins in.

When you’re someone who has played a long-running character like Vampire Bill on “True Blood,” is it difficult to escape some of the mannerisms from that role when you’re playing an entirely different character in a whole new universe in a play like this?

That’s a great question. Nobody’s asked me that. Look, I think however extraordinary Meryl Streep is, when she’s playing a part she’s still Meryl Streep. You don’t go like, that’s not Meryl Streep that’s George London, you know what I mean? However amazing Judi Dench is, you don’t not go that’s Judi Dench up there being a character. So I think it’s very hard to get away from your own mannerisms, the things you do in your every day life. There are some things that you can bring that are specific to that character. But ultimately it’s you up there. So I’m sure that the critics of this world will see all sorts of things that they want to see inside it. But I’ve built the character from the ground up, and to me, he’s nothing like Bill. But I’m sure people will make their own conclusions.

Is there a moment in the show that you fear? That you think will be tough to pull off live without making a mistake?

There’s a a couple. Obviously ”Edelweiss” is one because I’m playing and singing and it’s just me.

So after “Sound of Music Live!” ends, you’ve got to go end “True Blood.” That’s a lot of letting go.

Would you believe I start prepping on Monday? I fly back to L.A. and I’m up at 6 a.m. in the morning because I’m directing the first ep. So it’s pretty intense.